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Aims: the aim of this study was to extract gelatin from the skin of farmed great sturgeon at different temperatures, hydrolysis using Alcalase enzyme, and to measure molecular weight distribution of peptides, amino acid composition and antioxidant activity of hydrolysates.
 
Materials & Methods: After removing pigments and non-collagenous proteins, defatting, and swelling of triple-helix structure, gelatin was extracted at temperatures of 50, 60, 70 and 80 ºC for 6 h and then hydrolysed using Alcalase (E/S ratio of 1:20 w/w) for 3 h. Molecular weight distribution of peptides, amino acid composition and antioxidant activity of hydrolysates were determined.
 
Findings: Degree of hydrolysis reached its maximum within the first 30 min. Hydolysate from extraction temperature of 80 ºC had the highest DH.  No significant differences were found among hydrolysates with regards to amino acid composition and peptide molecular weight distribution. At of 60 ºC, the content of small peptides (< 1 kDa) and amino acids were slightly higher compared to other samples. This could influence antioxidant activity to some degree. At higher extraction temperature of gelatin, the efficacy of hydrolysates in preventing the loss in total sulfhydryl groups content was decreased (P < 0.05) while TBARS and surface hydrophobicity were not influenced (P < 0.05).
 
Conclusion: Extraction temperature of gelatin did not reveal a considerable effect on properties and antioxidant activities of the resulting hydrolysates and gelatin hydrolysates with antioxidant activity and rich in peptides with molecular weight less than 1 kDa could be produced at 50 ºC.

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In this experiment, head wastes were prepared and enzymatically hydrolyzed using alcalase (2.4 L) enzyme. The hydrolysate was fractionated by ultrafiltration with 10 kDa molecular weight cut-offs and the desired fraction was encapsulated following ion coagulation method (chitosan and triphosphate (TPP)) in nanochitosan capsules. Encapsulation process was optimized based on different ratios of chitosan:TPP and different concentrations (1, 5 and 10 mg/ml) of peptidic fraction. Finally, the degree of hydrolysis and the length of the peptides obtained from enzymatic hydrolysis were determined. The nanocapsules were examined for size, zeta potential and polydispersity index (PDI) using dynamic light scattering (Malvern, England). Structural and surface morphology studies including scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) of capsules produced under favorable conditions were also performed. Particle size was measured in various concentrations and treatments in the range of 30 to 150 nm. The best results were obtained in the treatment of 2: 1 ratio of chitosan to polyphosphate and concentration of 10 mg / ml. The size, dispersion index, zeta potential and size of nanocapsules in the optimal conditions were 0.375, 2020 and 30.13 nm, respectively, and storage conditions at -20 °C had no effect on the quality of nanocapsules. Based on the efficiency study, it was found that fraction with a concentration of 10 mg/ml is well encapsulated by chitosan with an efficiency of 91.04 ± 0.18 percent. The results showed that chitosan-TPP could be used for nanocapsulation of bioactive peptides with an approximate molecular weight of less than 10 kDa.

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Polysaccharides are one of biomacromolecules that, in addition to their peculiar physicochemical properties, possess promising biological capabilities depending on chemical structure. The objective of the present study was to evaluate the effect of molecular weight of galactofucan polysaccharides from freshwater plant Azolla filiculoides on its ability to stimulate RAW264.7 macrophage cells and inhibition of oxidation reactions. Galactofucan polysaccharide was extracted by distilled water at 65°C for 2 hours and recovered using 70% ethanol. Polysaccharide hydrolysis was performed using 0.01N HCl at 100°C for 5, 10 and 15 minutes. Crude and hydrolyzed polysaccharides were mainly composed of neutral sugars (67.46-68.02%), lower amounts of uronic acids (4.48-4.53%) and ranged in the molecular weight of 99.4-783.0 × 10³ g/ mol. Crude and hydrolyzed polysaccharides were non-toxic and hydrolysis 15 resulted in the greatest stimulation of proinflammatory response in RAW264.7 macrophage cells releasing a considerable amount of nitric oxide (55.6 μmol) into culture medium. Hydrolysis 15 led to the highest DPPH radical scavenging (65.2%) and Fe³⁺ reducing power (0.5 Abs). Overall, the present findings indicated that galactofucan polysaccharides have the ability to boost immune system and inhibit oxidation reactions and that molecular weight reduction to specific levels could improve the biological activities. 

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In this study, the orangefin ponyfish (Leiognathus bindus) was hydrolyzed by alcalase in an enzyme to substrate ratio of 1: 100 for 300 minutes, and the degree of hydrolysis was measured for 5 hours. Also, the hydrolysate was fractionated by centrifugal having molecular mass cutoffs of 3, 10, and 30 kDa, and four peptide fractions were obtained. Then, the antioxidant activity (DPPH and ABTS free radicals scavenging activity) of peptide fractions, as well as hydrolysate, were measured at different hydrolysis times. The degree of hydrolysis was the highest (55.43 ± 2.11%) at a hydrolysis time of 240 minutes. The hydrolysate had a high amount of hydrophobic amino acids (50.6%) which cause antioxidant properties. The results of DPPH radical scavenging activity showed that the highest scavenging activity was obtained at a hydrolysis time of 240 minutes (75.59 ± 1.46). Also, among all the fractions, the 3-10 kDa fraction exhibited the highest scavenging activity compared to other fractions (80.58 ± 2.96% at a concentration of 5mg /ml). Based on the result of ABTS radical scavenging, the highest activity was reported at 240 minutes after hydrolysis (50.54 ± 0.63). Also, among all peptide fractions, the 3-10 kDa fraction had significantly higher scavenging activity than other fractions (84.58 ± 0.44 at a concentration of 5 mg /ml). The results of this study showed that the peptides obtained by enzymatic hydrolysis of orangefin ponyfish are a good candidate for providing antioxidant properties.

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The aim of the current study was the evaluation of stepwise recovery of fucoidan extracted from seaweed Nizamuddinia zanardinii and the assessment of relationship between sulfate content and molecular weight with its antioxidant activity. After the removal of pigments and low molecular weight compounds, fucoidan extracted with water was precipitated using different concentrations of ethanol at three levels (30, 50 and 70%). Three fractions of Fuc30, Fuc50 and Fuc70 showed molecular weights of 731.62, 655.76 and 10.41 × 10³ g/mol, respectively. The content of sulfate esters in the obtained fractions were measured between 6.49-25.03%. The color evaluation of produced fucoidans by a digital chroma meter indicated the highest lightness index for Fuc50 fraction. Antioxidant results were varying in DPPH radical (43.93-89.40%) and ABTS radical (25.05-96.10%) scavenging activities as well as Fe³⁺ reducing power (Abs of 0.142-0.259). Overall, the findings of the present study indicated that stepwise precipitation of fucoidan from N. zanardinii leads to production of fractions with different chemical and molecular weight characteristics and antioxidant activities. Besides, although all isolated fucoidan fractions are introduced as potent antioxidant compounds, polymers possessing lower molecular weight and greater sulfate content exert higher antioxidant activities.
 

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Zebrafish is considered as a useful laboratory model due to its diverse characteristics, including self-renewal. The embryo of this fish has unique characteristics in the early stages of development, and its effects were observed in various studies. The differentiating factors present in stem cells isolated from zebrafish embryos are effective in improving the functional status of patients, and exposure to zebrafish embryo extracts in the early stages of development may increase the expression of multipotent stem cells and exert positive effects.  In this study, we investigated the antioxidant properties of the zebrafish embryo extract in different embryonic stages of development.The Zebrafish egg extract was prepared in different embryonic stages. Its effect in concentrations of 0.5, 1, 1.5 and 2 mg/ml on DPPH free radical scavenging activity, ABTS radical inhibitory activity and iron reducing power (FRAP) were investigated. The studied groups included protein extracts in morula, blastula and gastrula stages. According to the obtained results, the amount of protein varied in different embryonic stages and the amount of protein increased with the progress of fetal growth and the amount of fat decreased.The protein extract in the gastrula stage showed the highest level of DPPH inhibition and iron ion reduction at a concentration of 2 mg/ml compared to the morula and blastula groups (P<0.05). Also, the protein extract in the embryonic stage of blastula had the highest inhibition of ABTS at a concentration of 2 mg/ml compared to other groups (P<0.05).

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ABSTRACT
The aim of this study was to produce protein isolates from the head of the Siberian sturgeon (Acipenser baerii) and study its functional and structural properties. Fish protein isolates were prepared by the pH shift method using alkaline pHs 10.5, 11, 11.5, 12, and 12.5. The results showed that the efficiency of protein extraction and its amount of essential amino acids at pH 11.5 were higher than other treatments. Furthermore, the results of determination of functional properties such as Water Holding Capacity, Oil Holding Capacity, emulsifying properties, foaming and solubility of the isolated proteins showed that as the pH increased, the functional properties improved and the protein isolates at pH 11.5 compared with other treatments was significantly higher. (p < 0.05). Comparison of the color characteristics (L, a and b) of the isolated proteins showed at pH 12 were more bright (higher L parameter) than those isolated in other treatments tested. In addition, the amount of red (parameter a) and yellowness (parameter b) of the isolated proteins decreased with increasing pH. The results of the organoleptic examination of the smell and taste of protein isolates at pH 11.5 are the most common among other treatments. According to the observed cases, the results show that the resulting Siberian sturgeon isolate protein has favorable functional properties and that the use of alkaline pH changes can lead to improved functional properties and parameters of color protein isolates.

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In recent decades, the aquaculture industry has experienced a growing trend. In this regard, rainbow trout (Oncorhynchus mykiss) is known as one of the most popular species in the world and in Iran, with Iran ranking first in the production of this fish with an annual production of about 237,710 tons. After processing this fish, about 30% of it is considered as processing residue, which includes head, bone, viscera, etc. In the present study, a mixture of minced head and backbone waste from this fish was used to extract glycosaminoglycan using the alkaline dissolution method. The results showed that the extraction yield, carbohydrate, sulfate, uronic acid and protein content of the extracted glucosamine-glycan sample were 1.96 ± 0.14, 59.67 ± 3.66, 10.19 ± 0.38, 7.76 ± 0.20 and 11.23 ± 1.43%, respectively. Additionally, the infrared spectroscopy (FTIR) analysis of the obtained sample indicated the presence of broad peaks in the range of 3200 to 3600 cm^-1 and 2700 to 3000 cm^-1, corresponding to the functional groups –OH and the stretching band C-H, and the bending band of sulfate S=O at 1245 cm ^-1. Furthermore, the stretching band of the functional group COO-, related to the presence of uronic acid in the extracted sample, was observed in the range of 1480 to 1640 cm ^-1. The peaks appearing at 1385 and 11450 cm ^-1 were related to the stretching band O-C=O and the stretching vibration –CO in the COOH group.